Electrodeposition of Ag-Ni films from thiourea complexing solutions

Ag-Ni alloy films were electrodeposited from thiourea-based acidic solutions. Electrochemical studies confirmed the strong polarization of Ag deposition due to the strong complexation of Ag with thiourea, bringing the onset of Ag and Ni deposition closer, potentially favoring alloy formation. The as-deposited films were very fine grained (less than 20 nm) and consisted of various phases: a supersaturated solid solution of Ni in Ag and a Ni-rich nanocrystalline or amorphous phase, preferentially formed at grain boundaries. Ag-rich films were smooth, while a higher Ni content resulted in increasingly rough and porous films. Decomposition of the metastable phase and precipitation of the pure elemental phases occurred upon thermal annealing at 600 degrees C. Reduction of thiourea induced by Ni deposition led to sulfur incorporation in the films, up to 20 at.%. (c) 2012 Elsevier Ltd. All rights reserved.